Cellulose microfibril crystallinity is reduced by mutating C-terminal transmembrane region residues CESA1(A903V) and CESA3(T942I) of cellulose synthase

TitleCellulose microfibril crystallinity is reduced by mutating C-terminal transmembrane region residues CESA1(A903V) and CESA3(T942I) of cellulose synthase
Publication TypeJournal Article
Year of Publication2012
AuthorsHarris DM, Corbin K, Wang T, Gutierrez R, Bertolo AL, Petti C, Smilgies DM, Estevez JM, Bonetta D, Urbanowicz BR, Ehrhardt DW, Somerville CR, Rose JKC, Hong M, DeBolt S
Journal TitleProceedings of the National Academy of Sciences of the United States of America
Volume109
Pages4098-4103
Date Published03
Type of ArticleArticle
ISBN Number0027-8424
Accession NumberWOS:000301426700022
KeywordsArabidopsis, biosynthesis, cell wall, complexes, higher-plants, hydrogen-bonding system, microtubules, neutron fiber diffraction, PLASMA-MEMBRANE, polysaccharide, quinoxyphen, resistance, synchrotron x-ray
Abstract

The mechanisms underlying the biosynthesis of cellulose in plants are complex and still poorly understood. A central question concerns the mechanism of microfibril structure and how this is linked to the catalytic polymerization action of cellulose synthase (CESA). Furthermore, it remains unclear whether modification of cellulose microfibril structure can be achieved genetically, which could be transformative in a bio-based economy. To explore these processes in planta, we developed a chemical genetic toolbox of pharmacological inhibitors and corresponding resistance-conferring point mutations in the C-terminal transmembrane domain region of CESA1(A903V) and CESA3(T942I) in Arabidopsis thaliana. Using C-13 solid-state nuclear magnetic resonance spectroscopy and X-ray diffraction, we show that the cellulose microfibrils displayed reduced width and an additional cellulose C4 peak indicative of a degree of crystallinity that is intermediate between the surface and interior glucans of wild type, suggesting a difference in glucan chain association during microfibril formation. Consistent with measurements of lower microfibril crystallinity, cellulose extracts from mutated CESA1(A903V) and CESA3(T942I) displayed greater saccharification efficiency than wild type. Using live-cell imaging to track fluorescently labeled CESA, we found that these mutants show increased CESA velocities in the plasma membrane, an indication of increased polymerization rate. Collectively, these data suggest that CESA1(A903V) and CESA3(T942I) have modified microfibril structure in terms of crystallinity and suggest that in plants, as in bacteria, crystallization biophysically limits polymerization.

URL<Go to ISI>://WOS:000301426700022
DOI10.1073/pnas.1200352109
Alternate JournalProc. Natl. Acad. Sci. U. S. A.